https://glowfic.com/posts/7239
The six female marriage candidates are Abigail, Emily, Haley, Leah, Maru, and Penny. Meeting them involves having a conversation where both they and Oliver say something to each other--merely seeing them at the Flower Dance or walking thru town or so on doesn't count. (The level of interaction here counts as meeting Elliot, even tho Oliver didn't directly address him.)
"Picking one" means giving them a bouquet, not forming a verbal intention to date them. If the bouquet is accepted (even by a bachelor or non-candidate NPC), the market will resolve based on the list of 6; if the bouquet is rejected, the market will only resolve if it was rejected by one of the 12 candidates. (Attempting to give the bouquet to Pierre as a test, for example, will not resolve the market.) Establishing that more than those 12 people can be dated in-story will not adjust the resolution criterion for this market.
Related questions
@April hmm good questions
1) it will resolve YES if he meets all 6 candidates, even if he doesn't later give anyone a bouquet.
2) it will resolve N/A if the story ends (or the market close time is reached) without either condition having happened.